The claim was made in the duke’s forthcoming autobiography Spare, which has been leaked ahead of its official publication on 10 January.
In the excerpt, Harry reportedly claims that the physical altercation took place at his London home in 2019 when his brother grabbed him by the collar, ripped his necklace off and “knocked” him to the ground.
Harry writes that during the argument that preceded the incident, William called Meghan “difficult”, “rude” and “abrasive”.
The Independent has approached Buckingham Palace for comment on Harry’s claims.
Since the Duke of Sussex’s autobiography Spare was accidentally put on sale in Spain on 5 January, five days before its official release date, excerpts from it have been continuously published by press around the world.
These sections contain stories ranging from the revelation that Prince Harry killed 25 people while serving in the military in Afghanistan to his experiences with drugs such as cocaine and magic mushrooms.